When Philadelphia Mayor Michael Nutter took office in January 2008, he pledged in his inaugural address to make this 6th largest city in the US, the greenest city by 2015.
To do so, he created the Mayor’s Office of Sustainability and redesigned city government, appointing a team of deputy mayors to oversee and coordinate among departments.
After a year of research on municipal sustainability and conferring with residents and businesses, Greenworks Philadelphia was released in 2009. The ambitious plan sets 15 sustainability targets in the areas of energy, environment, equity, economy, and engagement to make Philadelphia the greenest city in America by 2015, including:
- Reduce city government energy consumption 30%; citywide building energy consumption 10%
- Retrofit 15% of housing stock with insulation, air sealing and cool roofs
- Buy or generate 20% of electricity from renewable energy sources
- Reduce greenhouse gas emissions 20%
- Diverting 70% of solid waste from landfill
- Providing park and recreation resources within 10 minutes of 75% of residents
- Bring local food within 10 minutes of 75% of residents
- Increase tree coverage 30% in all neighborhoods by 2025
- Reduce vehicle miles traveled 10%
• Double the number of green jobs.
Greening Storm Water Infrastructure
The City’s 719-page “Green City, Clean Waters” plan for managing the first inch of rainwater in a storm event via green infrastructure is considered the model for the country.
By replacing concrete with green landscaping and other pervious surfaces, it will not only control flooding and storm water surges, it will also reduce greenhouse gas emissions (plants and soil sequester carbon), provide more park and recreation resources, increase tree coverage, make the city more bicycle and pedestrian friendly, and create green jobs.
An investment of $1.6 billion over 20 years will keep storm water out of our systems by recreating the natural systems that centuries of urbanization have degraded, says Mayor Nutter. The alternative, he says, is to increase the city’s storm water capture and storage capacity at an estimated cost of about $10 billion.
The goal is to transform 9500 acres of impervious cover – about half of the total drainage area – into green acreage, and to restore 20 miles of urban stream corridor. Technologies include pervious pavement, green roofs, rain barrels, storm water tree trenches, vegetated bump-out curb extensions and rain gardens.
Every time it rains, a significant amount overflows the sewage system, sending sewage and other pollutants into rivers and streams. The idea is to manage storm water before it reaches the wastewater infrastructure and to reduce demand through reuse, recycling and infiltration. That allows the existing infrastructure to handle it.
Philadelphia is not a rich city – this plan also makes it attractive and livable.
After three years of mapping and conducting an equitable-cost-of-service analysis that assigns a value to storm water management, Philadelphia changed the way it bills for storm water. Instead of being meter based it’s based on impervious area. Private landowners who reduce impervious areas can receive credits up to nearly 100% on their storm water bill.
The EnergyWorks initiative, supported by a $25 million grant from the U.S. Department of Energy’s Better Buildings program, provides, free energy audits and very low interest loans (under 1%) for energy retrofits. The city also hired an Energy Manager to focus on policy and an Energy Conservation Coordinator to promote awareness of energy conservation among city employees. Funds from the Recovery Act also contributed to efficiency upgrades and including an energy management system for the city. Legislation passed which requires all new construction to meet or exceed Energy Star cool roof standards.
Harvesting Energy from Wastewater
Water Department Commissioner Neukrug sees wastewater plants more as resource recovery facilities these days. Water pumping, wastewater treatment and storm water management combined account for 40% of the municipal government’s energy use.
The Northeast Wastewater Treatment Plant, which processes 190 million gallons of wastewater daily, is receiving de-icing fluid from Philadelphia’s International Airport across the street and adds it to anaerobic digesters to boost methane production. “The airport saves roughly $100,000 a year, and we make $100,000 a year,” he says.
Another waste-to-energy strategy they’re looking at is adding co-digestion of food waste to boost methane production at the wastewater plant. They can also make biodiesel from sludge and scum. They plan to install a 5.6 megawatt (MW) cogeneration plant that will supply 86-100% of the energy demand. The wastewater plant will become a net producer of energy over the next 20 years, he says.
The Water Department is also working on a demonstration project to use sewer geothermal technologies to heat and cool one of its 20,000 square-foot compressor buildings. “In China for the Olympics it was used to heat and cool the Beijing train station,” says Crockett of the Water Dept.
“The concept is very similar to ground geothermal, because the fluid in sewers is typically a constant temperature as is the ground and thus can be used as a heat source or sink for heating and cooling a building from a thermodynamic perspective.” The only issue hindering widespread use of sewer geothermal is the separation of the material in sewage that could foul and impact the heating/cooling pump system, he explains, adding that recent improvements in the reliability and performance of those separation technologies are making it more appealing.
Other water treatment plants are using solar panels. “After we finish getting the Northeast cogen and southeast solar projects off the ground, we will be turning our attention to taking the land on top of our finished water storage at the Baxter Water Treatment Plant and using it to lease space for a 2 to 5 MW solar farm.”
If built, this system would be able to provide enough energy to treat and deliver half the city’s drinking water during a sunny day. “That project would take us one step closer to being able to deliver a ‘glass of sunshine’ to our customers,” he notes. “In fact, we call that our “Glass of Sunshine” initiative.”